USPTO Patents Application 10004917

a PATENT SPECIFICATION <»> 1 350 530

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(21) Application No. 26161/72 (22) Filed 5 June 1972

(31) Convention Application No. P 21 27 685.7

(32) Filed 4 June 1971 in

(33) Germany (DT)

(44) Complete Specification published 18 April 1974

(51) International Classification F15B 1/04

(52) Index at acceptance

FID P18A

(19)

(54) ARRANGEMENTS FOR DAMPING PRESSURE OSCILLATIONS

(7 1 ) We, Daimler-Benz Aktien-
geseixschaft, a Company organised under
the laws of Germany, of P.O. Box 202, 7000
Stuttgart 60, Germany, do hereby declare
5 the invention, for which we pray that a
patent may be granted to us, and the
method by which it is to be performed, to
be particularly described in and by the fol-
lowing statement: —

10 The invention relates to apparatus for
damping pressure oscillations which are
transmissible to a column of liquid in a
duct and having a damping vessel in which
the liquid is separated by a metal diaphragm

15 from an air column.

When liquids flow in pipes it is possible as
a result of superimposed pressure fluctu-
ations for generated sound or "hammer" to
be introduced and transmitted to other com-

20 ponents. These pressure fluctuations which
are superimposed on the static pressure can,
for example, be brought about by a pump
which is designed as a gear pump or rotary
pump or can be transmitted to the liquid

25 column by the sound oscillations or vibra-
tions of a unit with a motor to which a
pipe or the pump is fixed.

It is known that these superimposed pres-
sure oscillations can be damped by the

30 incorporation of damping vessels in which
an air volume is separated from the liquid
by a diaphragm.

In the case of a heavily fluctuating static
pressure, however, it is only possible for the

35 diaphragm to be correctly designed and
adjusted for a given working range.

The invention seeks to provide an im-
proved damping device in which the damp-
ing properties of the metal diaphragm can

40 also be adjusted to an optimum in extreme
cases.

According to the invention there is pro-
vided a damping device for damping pres-
sure oscillations which are transmitted to a
45 column of liquid contained in a duct,
wherein said device comprises a damping
vessel having a damping chamber connected
to said duct and separated from a closed
air chamber by a metal diaphragm and Juhe
{Price 25p] ~

air chamber is provided with resilient means 50
disposed on the side of said air chamber
remote from said metal diaphragm which
act in opposition to deflections of the metal
diaphragm caused by said pressure oscil-
lations. 55

In one embodiment of the invention a
spring loaded buffer is provided in the
damping vessel against which the diaphragm -
rests when the pressure in the liquid exceeds
a pre-determined limit. The buffer can be 60
pressed in the direction of the diaphragm
by a spring, the other end of which rests on
the part of the damping vessel containing
the air column.

In a further feature of the invention the 65
buffer forms part of a piston which is moun-
ted in the damping vessel and is also acted
upon by the liquid pressure on the part of
the piston remote from the buffer. When
this is done, the piston can be pressed by a 70
compression spring against the pressure of
the liquid.

The air column which is in an air chamber
sealed on one side by the metal diaphragm
can be sealed on its other side by a rubber 75
diaphragm with a suitably sealected factor
of flexibility or stiffness, which is acted upon
also by the liquid pressure on the side oppo-
site the column of air.

. Embodiments of the invention will be ex- 80
plained in greater detail in the description
which follows by way of examples and with
reference to the accompanying drawings, in
which: —

Figure 1 shows a diagrammatical repre- 85
sentation of a longitudinal section through
a damping vessel with a buffer and a spring.

Figure, 2 is a longitudinal section through
a damping vessel with a buffer connected to
a piston, which is acted upon by the liquid 90
pressure on its side remote from the buffer.

Figure 3 shows a section through a damp-
ing vessel in which an air chamber is sealed
on one side by a metal diaphragm and on
the other side by a rubber diaphragm. 95

The device for damping pressure oscil-
lations which can be transmitted to a liquid
column located in a pipe shown in Figure 1

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consists of a damping vessel 1, in which
there is fixed a metal diaphragm 2 which
defines one side wall of a damping chamber.
The damping vessel has a union 3 to which
5 there is connected the liquid column which
under certain circumstances is subjected to
pressure fluctuations which are transmitted
to the damping chamber. On the other side
of the diaphragm 2 is a sealed air chamber

10 7 in which there is arranged a buffer 4,
against which the metal diaphragm can rest
when the pressure in the column of liquid
rises above a predetermined level. As shown
in Figure 1, the buffer or stop 4 is designed

15 with contact contours which can be adapted
to particular requirements. When the static
pressure rises sufficiently, the diaphragm 2
rests ^on the contact surface of the buffer 4
located on the air chamber side and in this.

20 way becomes pressure-resistant. The buffer
itself is supported resiliency against the
housing by one end of a spring 5 the other
end of which rests on the bottom 6 of the
part of the damping vessel 1 which contains

25 a volume of air. The spring 5 is selected
so that it will provide the requisite adjust-
ment of frequency.

As shown in Figure 2, the buffer 8 can
also form one end of a piston 9 which is

30 slidably mounted in the damping vessel 11.
The column of liquid 12 in the damping
chamber acts on the diaphragm 2 and the
buffer 8, the piston 9 extending into the
connection 18 through the air chamber 17

35 on the side of the diaphragm 2 remote from
the liquid 12.

The piston 9 is mounted in two bores 13
and 14 in the damping vessel 11 so that it
can move along its longitudinal axis. These

40 bores 13 and 14 are located in two partitions
15 and 16, the partition 16 sealing the air
chamber 17 in relation to the liquid column
12, which acts through the union 18 into
of the piston 9. In order to increase the

45 volume of air, the partition 15 can be pro-
the damping chamber and through the union
19 on the damping vessel 11 against one end
vided with apertures. A disc 21 is mounted
on the piston 9, which is secured against

50 longitudinal movement and on which rests
one end of a spring 22, the other end 23 of
which rests against the partition 15.
Accordingly the spring 22 presses the piston
9 against the pressure in the liquid column

55 acting through the union 18.

As a result of the static pressure acting
on both sides of the cylinder as shown in
Figure 2, the diaphragm 2 is supported from
the rear. Here again the contour of the

60 buffer 8 can be designed differently accord-
ing to conditions. By suitably adjusting the

spring 2 it is possible for the pressure oscil-
lations to be kept away from the rear of the
diaphragm or else by suitable phase rotation
it is possible for the action of the diaphragm 65
to be increased still further.

Figure 3 shows a damping device 24 in
which the air column 25 is sealed at one
end by the metal diaphragm 2 and at the
other end by a rubber diaphragm 26 with 70
a suitably chosen spacing constant or rale.
Like the metal diaphragm 2, this rubber dia-
phragm is acted upon on its side which is
remote from the air column by the pressure
of the liquid column 27. which is connected 75
to the unions 28 and 29. The stiffness of
the rubber diaphragm 26 must be designed
in such a way that the requisite differential
pressure between the liquid column 27 and
the air column 25 is obtained. 80

WHAT WE CLAIM IS :—

1. A damping device for damping pres-
sure oscillations which are transmitted to a 85
column of liquid contained in a duct, where-
in said device comprises a damping vessel
having a damping chamber connected to said
duct and separated from a closed air cham-
ber by a metal diaphragm and the air 90
chamber is provided with resilient, means
disposed on the side of said air chamber re-
mote from said metal diaphragm which act

in opposition to deflections of the metal dia-
phragm caused by said pressure oscillations. 95

2. Device according to claim 1 wherein
the resilient means comprises a resilient
buffer arranged in the damping vessel and
against which the metal diaphragm is sup-
ported when the pressure in the liquid 100
column exceeds a pi^etennined level.

3. Device according to claim 2, wherein
the buffer is pressed in the direction of the
metal diaphragm by one end of a spring, the
other end of which rests on a part of the 105
damping vessel containing the air column.

4. Device according to claim 2 or claim
3, wherein the buffer forms one end of a
piston which is mounted in the damping
vessel and is acted upon by the liquid pres- 1 10
sure on its other end which is remote from >>
the buffer.

5. Device according to claim 4, wherein
the piston is pressed by a compression spring
against the liquid pressure acting on said 115
other end.

6. Device according to claim 1, wherein
the air chamber is sealed on one side by
said metal diaphragm and is sealed on its
other side by a rubber diaphragm having a 120
predetermined spring rate or constant which

is also acted upon by the liquid pressure on

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its side remote from the air chamber.

7. A device for damping pressure oscil-
lations substantially as hereinbefore des-
cribed with reference to Figure 1 or Figure
2 or Figure 3 of the accompanying draw-
ings.

JENSEN & SON,
Agents for the Applicants,
8, Fulwood Place,
High Holborn,
London, WC1V 6HG.
Chartered Patent Agents.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd.— 1974.
Published at The Patent Office, 25 Southampton Buildings, London WC2A 1AY,
from which copies may be obtained.

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